Paper-making is a multiple step operation, involving forming, pressing, drying and reeling. A paper web is formed from a stock slurry in the forming section and is pressed and dried to a final paper sheet, which then is reeled up into large rolls of paper.
Modern paper-making machines operate at high speed and economy of operation requires continuous production of paper sheet, so that the reeling operation must be able to switch smoothly from a fully-wound roll to an empty reel, with only a minimal loss of paper.
Reeling operations generally involve a driven reel drum, and a winding reel, or reel spool, which is driven by engagement with the paper sheet passing in contact with the reel drum. The winding reel usually is supported on rails during the reeling operation. Tension is provided to the paper sheet by running the driven reel drum faster than the speed of the previous section of the paper-making machine, while nip load is provided between the winding reel and the driven reel drum. The tension and nip load can be varied, within rather narrow limits, to produce rolls of paper with a desired tightness.
As one winding reel forms a paper roll, an empty winding reel is positioned adjacent but not engaging the driven reel drum upstream of the operating winding reel. As the operating winding reel grows in diameter, the empty winding reel is rotated to the same surface speed as the driven reel drum, by any suitable starting drive.
Support arms then move the empty winding reel into engagement with the paper web passing over the surface of the driven reel drum, and the paper web then is cut, so that the paper web then follows and is wound up on the empty winding reel, with little or no paper being lost in the changeover.
The paper roll, or jumbo, is removed from its support rails while the new winding reel is moved onto the support rails vacated by the paper roll. A new empty winding reel then is positioned upstream of the winding reel, to repeat the procedure.
As discussed above, tension and nip load are employed to produce rolls of paper with the desired degree of tightness. There are narrow limitations, however, since, if the tension and/or nip load are too low, then the jumbo roll is soft and prone to defects. If the tension is too high, a weak sheet breaks and paper-making machine production is stopped. If the nip load is too high, then the nip itself creates defects in the jumbo roll. Defects in jumbo rolls are highly undesirable and can lead to breaks during printing, which is highly inconvenient to the end-user.
Environmental considerations have lead to a recycling of a wide variety of paper products and the incorporation of recycled fiber in newsprint and other paper furnishes. The limitations referred to above with respect to conventional operations are particularly severe for newsprint containing large amounts of recycled fiber.
In particular, it has been noted that, in paper rolls formed from such materials, a zone adjacent each longitudinal end of the roll and immediately adjacent the winding reel surface tends to be soft and prone to give rise to defects, including crepe wrinkles and internal bursts. This has lead to the practice that, when the jumbo roll is rewound into smaller rolls for customer use, the portion adjacent the reel surface is discarded and recycled, thereby decreasing overall production.
A search in the facilities of the United States Patent and Trademark Office with respect to the present invention revealed the following U.S. Patents as the closest known prior art:
U.S. Pat. No. 2,248,014 PA1 U.S. Pat. No. 3,061,225 PA1 U.S. Pat. No. 4,729,522
It is noted that none of this prior art is concerned with the problem associated with handling a continuous paper web, as in the reeling operation of a paper-making machine. Rather each citation is concerned with a rewind device which processes a roll of paper in a batch operation.
In particular, U.S. Pat. No. 2,248,014 relates to an unwinding reel drive employing belts engaging the roll and a tension regulator for the unwinding roll by applying a braking force to the reel which is controlled by a speed regulator which compensates for changes in diameter.
U.S. Pat. No. 3,061,225 also relates to an unwinding mechanism, which also may be used for rewinding, which employs a belt drive. The patent describes a device for compensating for tension variations in the winding web. In addition, a supplementary torque is applied to the roll (via a pulley and belt), which causes that portion of the rewinding web closest to the spindle core tube to wind tightly around the tube. It is intended that the assist decrease with increasing diameter.
U.S. Pat. No. 4,729,522 also describes an unwinding device. The patent is directed to a mechanism for maintaining a constant web tension in the unreeling web. The tension is sensed and a roll-contacting belt is driven in response to the sensed tension. A positive drive means also is connected to the roll shaft in order to variably control the rotation of the roll responsive to the sensed tension. The belt is operated to control the tension in the web when the roll is larger while the positive drive means operates to control rotation of the roll when the roll is smaller.
Accordingly, this prior art describes a variety of devices which are employed in wind up and unwinding of rolls and which are intended to control web tension. None, however, is directed to the problems of a continuously-operating paper machine reeling operation nor the provision of a positive drive to the take-up reel during the initial stages of reel uptake, as required herein, and as detailed below.